Theoretical Study on Substituent's Effect on the Properties of Benzofused thieno [3, 2-b] Furan and its Isomeric Form

Abstract

ABSTRACT: The theoretical study on the ground state properties of isomeric benzofused thieno [3,2-b]furans was carried out using semi-emperical AM1 and Density functional theory/B3LYP 6-31G* /6-31G* basis set. This was used in order to determine the effect of substituent; Br 2 , I 2 , OH -, on the stability, reactivity and other properties of the isomers. From the calculated values of E, μ, η, ω, ΔH-L obtained, it can be inferred that thieno [3,2-b]benzofuran is more aromatic, more stable and less reactive than isomeric benzothieno[3,2-b]furan. These results agree with the experimental result concerning the different reactivity and stability of both heterocyclic systems. The study of bond order uniformity, local ionization energy and electrostatic potential energy surfaces analysis revealed structural differences of isomeric thieno [3,2-b]furans that explains their reactivity features. Benzothieno[3,2-b]furan could be an analogue of aromatic benzothiophene substituted with C(2)=C(3) vinylic moiety. This evidently points out therefore that the electrophilic substitution reaction for benzothieno [3,2-b]furan goes via addition-elimination mechanism at the C(2)